BQ25756E: questions about BQ25756E

Hello,

Thanks for working on this

?? ? said:

Does the charging curve of the chip when I use a constant voltage load as an output match the graph below?

The constant voltage load will work well during the BQ25756E's constant current phases. The constant voltage load will not work well during the BQ25756E's constant current phases. I recommend using a constant current load to test the taper charge phase.

1. Yes,

2. Yes, this will work.

3. Yes, you need a good VAC or VBAT voltage to write to the I2C registers.

4. (You've got 2 questions that are marked with "3"). Yes, you can read the registers by clicking "Read Registers". Make sure the device has the right I2C address first.

5. For a battery monitoring module, can you let me know what the charging current and charging voltage are? Also, do you need a battery fuel gauge or just an IC to balance and monitor the battery?

Best Regards,
Ethan Galloway

Hello,

Thanks for your reply!

I am trying to program the BQ25756E using bqstudio, but I am making the chip work with EV2400 recognized by bqstudio, and I am doing read register

operation in D4(6A) address, but the page is showing 'DEVICE ACK ERROR', I would like to ask how to solve the problem?

Ethan Galloway said:

5. For a battery monitoring module, can you let me know what the charging current and charging voltage are? Also, do you need a battery fuel gauge or just an IC to balance and monitor the battery?

Charging current:6A;Charging voltage:~26V.

I would like to know what exactly is the functional difference between a battery fuel gauge and an IC? Is it that a gauge can only monitor and not actively

regulate the charge balance of multiple batteries while an IC can monitor and regulate at the same time? If this is the case, is it possible that I can use only

one IC to realize the function of charging and balancing voltage and no longer need the BQ25756E, do you have any recommendation for this product?

Thanks in advance!

Hello,

Thanks for the new information.

?? ? said:

I would like to ask how to solve the problem?

I have a few suggestions:

• Make sure the IC has power.
• Make sure the EV2400 is plugged in before starting BQStudio
• Make sure the I2C lines have the correct pull ups.

Let me know if those work.

?? ? said:

I would like to know what exactly is the functional difference between a battery fuel gauge and an IC? Is it that a gauge can only monitor and not actively

A battery monitor provides protection, balancing, and monitoring for the battery. A battery gauge has the same features, but also gives a state of charge for the battery. A battery gauge can provide a percentage of the battery's lifespan.

?? ? said:

If this is the case, is it possible that I can use only

one IC to realize the function of charging and balancing voltage and no longer need the BQ25756E, do you have any recommendation for this product?

We don't anything that will work in the voltage or current range of your application. I think the BQ25756E + a battery gauge / monitor would work the best for your application.

Best Regards,
Ethan Galloway

Hello,

Thanks for your reply!

Ethan Galloway said:

I have a few suggestions:

• Make sure the IC has power.
• Make sure the EV2400 is plugged in before starting BQStudio
• Make sure the I2C lines have the correct pull ups.

All three of these conditions have been met so far. bqstudio has recognized the EV2400, SCL and SDA both have 3.3V pull-up voltages, and I have 6V DC

input to both VAC ports (32,33). But when I finish all this clicking on 'read registor' still shows 'device ACK error'.

I'm currently thinking that there is something wrong with my circuit setup because I'm currently reading the registers with a 6V input to the VAC, a low CE port,

and a 7V constant voltage load on the output, and the load side rises to 7V within 10s when I input the voltage, so is it possible that I'm getting a higher

voltage on the constant voltage load and thus failing to program the I2C? And the chip will start working after inputting VAC, is writing registers at this time

affecting the chip's operation? What do you currently feel could be the problem?

Ethan Galloway said:

We don't anything that will work in the voltage or current range of your application. I think the BQ25756E + a battery gauge / monitor would work the best for your application.

I have found one of your ICs - BQ76907, do you think this IC can work with BQ25756E so as to equalize charging for multiple Li-ion batteries?

Also, I would like to ask if the BQ76907 can be I2C programmed directly with the bqstuido using the EV2400 instead of the MCU chip?

Thanks in advance!

Hello,

When you apply voltage to the charger, can you try applying a 6V DC source to VBAT and see if that 's any different?

?? ? said:

and a 7V constant voltage load on the output, and the load side rises to 7V within 10s when I input the voltage, so is it possible that I'm getting a higher

voltage on the constant voltage load and thus failing to program the I2C?

I think this might be the charger operating with the default settings.

Can you check SDA and SCL with an oscilloscope to make sure the signals are being sent correctly?

?? ? said:

I have found one of your ICs - BQ76907, do you think this IC can work with BQ25756E so as to equalize charging for multiple Li-ion batteries?

Also, I would like to ask if the BQ76907 can be I2C programmed directly with the bqstuido using the EV2400 instead of the MCU chip?

I misread your question here. Battery monitors and battery gauges provide cell balancing and protection to the battery. These monitors and gauges can be programmed with I2C. I think the BQ76907 would work, but I would recommend opening an E2E thread on the battery monitor e2e forum.

We also have this brief app note on the difference between battery gauges and battery monitors: www.ti.com/.../sszt466.pdf

Best Regards,
Ethan Galloway

Hello,

Thanks for your reply!

Ethan Galloway said:

When you apply voltage to the charger, can you try applying a 6V DC source to VBAT and see if that 's any different?

I'll try it later.

Ethan Galloway said:

I think this might be the charger operating with the default settings.

That's what I thought too, but when the IC has power it starts working as per default settings. As I understand from referring to the BQ25756EVM file, the I2C

programming is to read and write register when the IC is working, and I am wondering if the 'ACK error' was generated because I clicked on 'Read Register'

without having written the initial value of the 16-bit registers in the figure below. Or is it that clicking 'Read Register' should be done in the '8 bit Register' page,

and then the corresponding register bit will show the corresponding register value of the current chip?

Ethan Galloway said:

but I would recommend opening an E2E thread on the battery monitor e2e forum.

Thanks,I'll post a new one on this forum.

Thanks in advance！

Ethan Galloway said:

Can you check SDA and SCL with an oscilloscope to make sure the signals are being sent correctly?

I can only observe 3.3V at SDA,SCL.

Hello,

?? ? said:

That's what I thought too, but when the IC has power it starts working as per default settings. As I understand from referring to the BQ25756EVM file, the I2C

programming is to read and write register when the IC is working, and I am wondering if the 'ACK error' was generated because I clicked on 'Read Register'

without having written the initial value of the 16-bit registers in the figure below. Or is it that clicking 'Read Register' should be done in the '8 bit Register' page,

and then the corresponding register bit will show the corresponding register value of the current chip?

When the charger first starts up, the registers are pre-written and the charger uses the hardware settings to determine the charge current, charge voltage, and other settings. Clicking "Read Registers" shouldn't cause 'ACK error'.

?? ? said:

I can only observe 3.3V at SDA,SCL.

I have a few other questions here:

• Do you see SDA and SCL being pulled down whenever you click read registers?
  
  
• Do you see any difference if you use the BQ25756E BQZ File? Both the BQ25756 and BQ25756E BQZ files should work.
• Have you tried changing the USB port the EV2400 is plugged into?

Best Regards,
Ethan Galloway

Hello,

Thanks for your reply!

Ethan Galloway said:

Do you see SDA and SCL being pulled down whenever you click read registers?

I tried again but I can't see any voltage change.I would like to ask if the EV2400 produces a voltage change when I click on 'Read Register' without connecting the chip? At the moment I don't see any voltage change with or without the chip connected.

Ethan Galloway said:

Do you see any difference if you use the BQ25756E BQZ File? Both the BQ25756 and BQ25756E BQZ files should work.

I installed the 'bqstudio-test' version with the BQ25756E BQZ file as follows.

Ethan Galloway said:

Have you tried changing the USB port the EV2400 is plugged into?

I did it too but it doesn't work either.

Thanks in advance!

Hello,

?? ? said:

I would like to ask if the EV2400 produces a voltage change when I click on 'Read Register' without connecting the chip?

Yes, you should see the SDA or SCL lines being pulled down when the EV2400 tries to communicate with the BQ25756E.

?? ? said:

I installed the 'bqstudio-test' version with the BQ25756E BQZ file as follows.

Can you install this file: https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/1379348/faq-bq25756e-bqz-file-for-bqstudio ?

And move the file to BQStudio's config folder? The default folder path should be C:\ti\BatteryManagementStudio

I have a few other questions to try to debug this:

• Is there anything else you can tell me about your system?
• Do you have any other EV2400s or EVMs to try to communicate too with BQStudio if possible?
• Can you try communicating with the EVM with a different computer?

Best Regards,
Ethan Galloway

Hello,

Thanks for your reply!

Ethan Galloway said:

Can you install this file: https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/1379348/faq-bq25756e-bqz-file-for-bqstudio ?

And move the file to BQStudio's config folder? The default folder path should be C:\ti\BatteryManagementStudio

I installed the file,changed the computer and tried again but still no work,I've decided to redesign the PCB circuit once again, as my current circuit is designed primarily for programming resistors. Since I only have one EV2400, I'm going to try another one. 

Before I redesign the circuit, I have the following questions:

1.Does the BQ25756E have to differentiate between PGND and AGND when designing the circuit?
2. Do the SDA and SCL pins of the BQ25756E need 10k resistors to connect to the EV2400?
3. Can you provide a PCB file for the BQ25756E?

Thanks in advance!

Hello,

1. No, you don't have to differentiate between PGND and AGND.

2.The SDA and SCL resistors will need the proper pull up resistors. 10kΩ pull up resistors to 3.3V will work when using the EV2400.

3. Here's the PCB file of the BQ25756EVM:BQ25756EVM_Design_Files.zip

Best Regards,
Ethan Galloway